1. Field of the Invention
This invention relates in general to color photography and in particular to a new and improved method of photographic color development. More specifically, this invention relates to color development with a color developing composition, containing a primary aromatic amino color developing agent and an hydroxylamine compound, which is protected against metal-complex catalyzed oxidation of the hydroxylamine compound.
2. Description of the Prior Art
The formation of color photographic images by the image-wise coupling of oxidized primary aromatic amino developing agents with color forming or coupling compounds to form indoaniline, indophenol and azomethine dyes is well known. In these processes, the subtractive process of color formation is ordinarily used and the image dyes customarily formed are cyan, magenta, and yellow, the colors that are complementary to the primary colors, red, green, and blue, respectively. Usually phenol or naphthol couplers are used to form the cyan dye image; pyrazolone or cyanoacetyl derivative couplers are used to form the magenta dye image; and acylacetamide couplers are used to form the yellow dye image.
In these color photographic systems, the color forming coupler may be either in the developer solution or incorporated in the light-sensitive photographic emulsion layer so that, during development, it is available in the emulsion layer to react with the color developing agent that is oxidized by silver image development. Diffusible couplers are used in color developer solutions. Non-diffusing couplers are incorporated in photographic emulsion layers. When the dye image formed is to be used in situ, couplers are selected which form non-diffusing dyes. For image transfer color processes, couplers are used which will produce diffusible dyes capable of being mordanted or fixed in the receiving sheet.
In addition to a primary aromatic amino color developing agent, photographic color developing compositions frequently contain an hydroxylamine compound which functions to protect the developing agent against aerial oxidation. They also generally contain a sequestering agent to stabilize the composition against precipitation of metal salts or hydroxides and against undesired decomposition reactions, such as the decomposition of the hydroxylamine compound to generate ammonia or amines. A variety of sequestering agents or combinations of sequestering agents have been proposed in the past for use in stabilizing photographic color developing compositions containing a primary aromatic amino color developing agent and an hydroxylamine compound. For example, sequestering agents described as being useful for this purpose include the 1,3-diamino-2-propanol tetraacetic acid of U.S. Pat. No. 2,875,049; the diethylenetriamine pentaacetic acid of U.S. Pat. No. 3,462,269; the combination of an aminopolycarboxylic acid and an aromatic polyhydroxy compound of U.S. Pat. No. 3,746,544; and combination of an amino-N,N-dimethylenephosphonic acid and a diphosphonic acid described in Research Disclosure, Volume 134, Item 13410, June 1975; the combination of an hydroxyalkylidene diphosphonic acid and an aminopolycarboxylic acid or of an hydroxylalkylidenediphosphonic acid and an aminopolyphosphonic acid of U.S. Pat. No. 3,994,730; the organic compounds having at least one phosphono group and at least one carboxy group in the molecule described in U.S. Pat. No. 4,083,723; the combination of an aminophosphonic acid and an aminocarboxylic acid described in Research Disclosure, Volume 170, Item 17048, June 1978; and the combination of an aromatic polyhydroxy compound and an aminopolyphosphonic acid compound of U.S. Pat. No. 4,264,716.
It is well known in the photographic art to include aromatic polyhydroxy compounds in photographic color elements as stabilizing addenda. Such use of these compounds is described, for example, in Kennard et al U.S. Pat. No. 3,236,652 issued Feb. 22, 1966. It is also common for trace amounts of metal impurities to be present in photographic elements. Thus, for example, trace amounts of metals such as iron and manganese are often present as impurities in gelatin.
During the processing of photographic color elements, both trace metal impurities and aromatic polyhydroxy compounds utilized as stabilizing addenda can be leached from the photographic element and accumulate as seasoning products in the developing solution. As a result, the aromatic polyhydroxy compound can form a complex with the trace metal impurity and this metal-complex has the undesirable property of catalyzing oxidation of the hydroxylamine compound. This renders the hydroxylamine compound ineffective with regard to its intended function of protecting the developing solution against aerial oxidation.
It is toward the objective of providing a means of developing photographic color elements, which contain trace metal impurities and also contain polyhydroxy compounds, without excessive loss of the hydroxylamine compound incorporated in the developing solution that the present invention is directed.